Dresden 2026 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 12: Focus Session: Tunable Correlations in van der Waals Quantum Materials I (joint session TT/DS/HL)

TT 12.6: Vortrag

Montag, 9. März 2026, 17:45–18:00, HSZ/0003

Interlayer electrodynamics of CDWs in van der Waals materials and heterostructures — Achyut Tiwari, Renjith Mathew Roy, Maxim Wenzel, Christian Prange, Bruno Gompf, and •Martin Dressel — 1. Physikalisches Institut, Universität Stuttgart

Layered transition metal dichalcogenides such as 1T-TaS₂, 2H-TaS₂ and their natural heterostructure 4H_b-TaS₂ provide a platform for studying interlayer coupling, orbital hybridization, and charge transfer that determine collective electronic phenomena, such as unconventional superconductivity and strong electronic correlations. Temperature-dependent infrared measurements of the in-plane and out-of-plane optical response of 1T-TaS₂ across its CDW-driven metal-insulator transition are combined with DFT calculations. We find that a quasi-1D instability that induces interlayer dimerization is responsible for the MI-transition. Furthermore, spectroscopic ellipsometry combined with an anisotropic Bruggeman effective medium approximation reveals that metallic domains evolve in a strongly anisotropic way and often extend along the out-of-plane direction as the transition proceeds.

When 1T-TaS₂ is stacked between 1H-TaS₂, forming a natural heterostructure of 4H_b-TaS₂, charge transfer occurs between the layers, that can be tuned with temperature, and which is related to the CDW in 1T-TaS₂ layer. We conclude that the phase transition in 1T-TaS₂ is inherently three dimensional, despite its layered structure, and that interlayer coupling is essential for its electronic structure and phase behavior both individually and in heterostructures.

Keywords: van der Waals materials; charge density wave; superconductivity; optical properties; interlayer coupling